Only a tiny fraction of sharks caught in the Atlantic – less than 1% – are under protection, even though most shark species are heading towards extinction, a report warns on Tuesday.

Officials from 48 Atlantic fishing countries are meeting in Istanbul this week to try to protect bluefin tuna, swordfish and other large fish.

But existing conservation efforts are only saving a tiny proportion of sharks, the report from the Oceana conservation group said.

"It's just the tip of the iceberg, and there are a lot of shark species, many of them vulnerable species, that are still being caught and killed," said Elizabeth Griffin Wilson, a senior scientist at Oceana.

Conservation groups at the International Commission for the Conservation of Atlantic Tuna (Iccat) meeting are pushing for a ban on the catch of porbeagle and silky sharks – which are at extreme risk – as well as catch limits on other species such as the shortfin mako shark.

Three quarters of the wide ranging shark now being caught in the Atlantic are under threat, the report said.

But Iccat countries to date have only limited protection for specific shark species such as the bigeye thresher, hammerhead and oceanic whitetip sharks.

There are no limits on the fishing of 15 Atlantic shark species even though some – such as the silky shark – are close to extinction.

The White House on Monday sought the Senate's approval for a new international treaty that would make it easier for countries to crack down on any illegal catches being brought to port. The state of Florida is expected to adopt new protection measures this week.

The European Union last week banned all fishing for porbeagle shark in the Atlantic and Mediterranean.

But it is a race against time. Sharks were not built for reproduction. They can take take years to reach sexual maturity, and produce only a few pups.